5 Supplements You May Need if You’re on the Keto Diet

The keto diet limits your intake of many foods, which means you might become deficient in key nutrients.

Following the ketogenic ("keto") diet means sticking to a high-fat, moderate-protein, low-carb meal plan. Eating that way puts your body in a state of ketosis, in which you burn fat instead of sugar for energy.

In actuality, healthcare providers developed the keto diet to treat epilepsy in the 1920s. Still, people have been using the keto diet as a weight-loss plan since then.

While fans rave about the pounds they've shed, health experts say there are potential drawbacks to the keto diet, such as the keto flu. Another downside is that you may develop deficiencies of some crucial nutrients typically found in foods banned or restricted under the keto diet.

So, if you are considering trying the keto diet, you might consider taking supplements to compensate for those lost nutrients. Although, as with any changes to your diet, consult a healthcare provider.

Why You Might Need Supplements on the Keto Diet

You may need to take supplements to meet your daily nutrient intakes with the keto diet. One of the long-term impacts of the keto diet on your health is nutrient deficiencies.

Being deficient in specific vitamins and minerals can adversely affect your health. For example, a magnesium deficiency may cause nausea, vomiting, and fatigue.

Your body uses the nutrients in your diet to carry out several processes. For example, calcium helps build and strengthen your bones and teeth. Without calcium, your risk of osteoporosis increases. Osteoporosis causes weak bones that fracture easily. Similarly, a vitamin D deficiency may increase your risk of osteomalacia, which causes bone pain and weak muscles.

Iron is another key nutrient. Without iron, your red blood cells shrink and lack hemoglobin, causing iron deficiency anemia. As a result, you may feel weak and lack energy. In some cases, iron deficiency anemia may weaken your immune system.

Lastly, fiber helps with digestion and keeps your bowel movements regular. Consuming insoluble fiber can prevent constipation.


Many high-magnesium foods, like whole grains, bananas, and beans, contain too many carbs to be keto-friendly.

Still, magnesium plays a key role in over 300 processes in your body, including:

  • Supports the function of your nerves and muscles
  • Keeps your immune system healthy
  • Regulates your heart rate
  • Strengthens bones
  • Maintains blood sugar levels
  • Produces energy and proteins
  • Has been shown to prevent and manage high blood pressure, heart disease, and diabetes

The National Institutes of Health advises that women get 310–320 milligrams of magnesium daily, while men get 400–420 milligrams. For the most part, people do not need magnesium supplements. High-protein diets, like the keto diet, supply enough magnesium to meet your goals.

Some keto-approved, magnesium-rich foods include spinach, broccoli, and kale. However, taking a magnesium supplement can make sure you cover your bases. 

Talk to a healthcare provider about taking a magnesium supplement. Too much magnesium may cause nausea, diarrhea, and stomach pain.


Many milk and dairy products don't work on the keto diet due to their carb levels. For example, non-fat milk has 12 grams of carbs per serving. In contrast, the keto diet typically limits your carb intake to 20–50 grams daily.

By limiting or avoiding milk products, you also limit your calcium intake. Generally, adults aged 19–50 need 1,000 milligrams of calcium daily. Women older than 51 have even higher calcium needs, at about 1,200 milligrams daily.

Calcium is the most abundant nutrient in your body and serves many purposes, like:

  • Strengthens your bones and teeth
  • Helps muscles and blood vessels contract
  • Releases hormones and enzymes
  • Supports the nervous system

Besides milk products, other foods with optimal calcium levels excluded or limited on keto include calcium-fortified orange juice and tofu. Instead, some keto-friendly sources of calcium include sardines and salmon with bones, kale, and broccoli.

Yet, if you find it hard to eat so many leafy greens or dislike fish, a calcium supplement can help. A healthcare provider can help determine how much calcium you need to supplement with based on your health needs.


Think of iron as the fuel that allows every cell in your system to function correctly. For example, iron makes hemoglobin, a protein that delivers oxygen from your lungs to different body parts. Also, iron aids your muscles in storing and using oxygen.

Men aged 19–50 need eight milligrams of iron daily, while women aged 19–50 need 18 milligrams. Also, pregnant people need 27 milligrams of iron daily. Without that much iron, you may feel lethargic and weak.

Many keto-approved foods contain healthy amounts of iron, such as beef and oysters. However, the keto diet excludes or restricts other sources of iron, like cereal, lentils, tofu, and beans. Leafy green vegetables, like kale and spinach, are also good plant sources of iron. However, the body does not absorb the type of iron in leafy green vegetables.

So, an iron supplement may be a good idea to ensure you get the right amount. As with other nutrients, consult a healthcare provider if you cannot meet your iron intake with your diet.

Vitamin D

Even if you're not on the keto diet, getting sufficient vitamin D is hard. The body makes vitamin D when you expose your skin to the sun. However, many people avoid direct exposure to the sun's ultraviolet (UV) rays to lower their skin damage and cancer risks.

Also, although vitamin D is found in milk and cereal, the keto diet limits those items due to their high carb counts.

Still, vitamin D is an essential nutrient with many key roles, such as:

  • Aids your body in absorbing calcium
  • Staves of bone diseases like osteoporosis
  • Supports your nervous, muscular, and immune systems

Adults aged 19–70 should aim for 600 international units of vitamin D daily. If you're on the keto diet, fatty fish, such as salmon and tuna, and eggs are good sources of vitamin D.

However, with so few food options, a daily vitamin D supplement can help. Check with a healthcare provider for the right amount based on your needs.


Fiber adds bulk to your meals. In other words, fiber satiates your appetite and helps manage your weight. Also, fiber aids digestion and keeps your bowel movements regular. According to the National Institutes of Health, women need 25 grams of fiber daily, while men need 38 grams.

However, most sources of fiber come from whole grains, fruits, and vegetables, all of which may not be keto-friendly. A lack of fiber also opens the door to health risks, such as an increased risk of heart disease and colorectal cancer.

Some keto-friendly fiber sources include:

  • Seeds and nuts
  • Coconut
  • Avocado
  • Spinach
  • Broccoli
  • Cauliflower
  • Berries

However, filling your entire diet with those vegetables can be tough. So, a daily fiber supplement could help you meet your goal. Talk to a healthcare provider about the best supplement and how much to take.

A Quick Review

The keto diet is a high-fat, moderate-protein, and high-carb weight-loss plan. However, one of the long-term impacts of the keto diet is nutrient deficiencies. Ensure you eat plenty of keto-friendly foods rich in magnesium, calcium, iron, vitamin D, and fiber. However, consult a healthcare provider about supplementation if you cannot meet your goals. 

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